With continuous development of science and technology, precise manufacturing equipment and precise measuring equipment represented by IC manufacturing equipment, high resolution electron microscopes, surface roughness testers, precise optical equipment and the like have been used more and more widely, and the precision thereof is more demanding than ever before. As important basic equipment for achieving high precision, a vibration isolation device can isolate influences of foundation and environment vibration on precise equipment, provide a “quite” working environment for vibration-sensitive equipment, and ensure normal operation of the precise equipment.
A traditional passive vibration isolation structure is generally a rigid helical spring or air spring, which, as rigid elements, cannot attenuate vibration at a natural frequency of a vibration isolation system, and in a situation where an external excitation frequency is equal to the natural frequency of the vibration isolation system, the vibration isolation system resonates, so that vibration amplitude of the load is enlarged, resulting in that the equipment cannot work normally and is even damaged. By adding a damper, enlargement of the amplitude at the natural frequency of the vibration isolation system may be reduced, but high frequency attenuation performance of the vibration isolation system will be deteriorated. Therefore, a general passive vibration isolator can give consideration to both transmissibility and high frequency transmissibility at the natural frequency only by selecting an optimal damping value. The performance of the passive vibration isolation system often cannot achieve the requirement of precise vibration isolation.
In an active and passive combined manner, the problem of insufficient passive vibration isolation performance can be solved. U.S. Pat. No. 5,844,664 (Publication Number) discloses a vibration reduction system, the vibration reduction system includes an air spring, a swing mechanism and a voice coil motor, a sensor in the vibration reduction system detects a vibration signal and sends the vibration signal to a controller, the controller calculates a control instruction and sends the control instruction to the voice coil motor, and the voice coil motor outputs a force according to the control instruction. As the output force is achieved through a control algorithm, the output force conducts attenuation only for vibration near the natural frequency, which does not affect high frequency attenuation performance. Although active vibration isolation performance of the vibration reduction system meets requirements, the vibration reduction system is complex in structure, needs energy supply, has lower reliability than the passive vibration reduction system, and is at an enormous cost.
A permanent magnet material has a wide hysteresis loop, high coercive force and high residual magnetism, is a material that can maintain constant magnetic property once magnetized, and is also referred to as a hard magnetic material. The permanent magnet material has high maximum magnetic energy product, high coercive force, high residual magnetic flux density, high residual magnetization and high stability, and is widely used in occasions of various actuators such as motors, valves, speakers, steering gears and aeronautical equipment. In a magnetic mechanism, compared with the electromagnet, the permanent magnet material has the following advantages: the permanent magnet material does not need to supply energy, is very compact in structure, is easy to maintain, has a low cost, and is easier to be accepted by users. The permanent magnet material has very high residual magnetic flux density and can produce a greater magnetic force under a small size, while the electromagnet is limited by the power of a driver, and under a great current, the electromagnet emits greater heat, and thus it is inappropriate to select the electromagnet in a magnetic mechanism where it takes a long time to output a force. Therefore, the permanent magnet material has great potential applications in precision machinery.